1. Field of the Invention
This invention relates plasma etching of vias between two conductor levels in a printed wiring board (PWB) wherein the conductor levels are separated by organic dielectric material.
2. Brief Description of the Prior Art
Vias which are formed in printed wiring boards are used as an electrical or thermal interconnect between two sequential layers. Generation of a blind via begins with formation of a layer of dielectric material and a layer of copper onto the board which already has a copper layer on the surface thereof. The top or exposed layer of copper is then coated with resist, imaged and etched to remove the copper where blind vias are desired. To form the connection between the sequential copper layers, the dielectric material is removed from under the etched copper opening using a known method. The board is then coated with a thin layer of copper on the surface and in the vias to make the electrical or thermal connection to the copper layer on the board.
The formation of the blind via in the dielectric material is generally accomplished by discrete laser drilling, this being possible on one or two boards at a time. Although this method produces high quality vias, it is extremely time consuming. Also, the required equipment is quite expensive and bulky. Due to the limited number of boards that can be operated upon by one piece of equipment, the amount of equipment required for processing large number of boards becomes substantial, providing a great economic as well as space burden. It is therefore apparent that a method and system for formation of such blind vias which is capable of doing so on many boards simultaneously and at lower cost is essential to provide the desired economic as well as space advantage.